This invention relates to a device for the parallel metering of a liquid. For this purpose, the device has a first body in which there are a main channel, secondary channels, one inlet, and outlets. The main channel is connected to the inlet, while the secondary channels are connected to one outlet at a time. Furthermore, the secondary channels are connected to the main channel. The first body for delivering the metered liquid has means for transferring pressure surges of a first pressure medium from a first chamber to the secondary channels. Each of these transfer means is connected to a secondary channel.
Such a device is known from document WO 99/42805. The device disclosed in this document for the parallel metering of a liquid of the initially mentioned type as the transfer means for transfer of the pressure surges which are imparted to the metered amounts of liquid for emptying the device has small channels which adjoin the secondary channels. All these channels which are made as transfer means discharge into a pressure surge collecting channel. This collecting channel is subjected to pressure surges from a device for producing pressure surges, which is located outside of the device for parallel metering of a liquid. The pressure surges are accommodated by the collecting channel and are routed via the channels which are made as transfer means to the secondary channels and thus to the metered liquids. In doing so, among others, due to the different distances of the transfer means to a pressure medium connection of the collecting channel, time differences in the action of the pressure surges on the metered liquids can occur. This can result in the first secondary channel or the first secondary channel arrangement consisting of an outlet and a secondary channel being emptied while other channels still contain the metered liquid. Sometimes this can be quite desirable, but if the first secondary channel or the first secondary channel arrangement is already emptied, the collecting channel is vented via the channel which is made as the transfer means and the secondary channel toward the inlet. The metered liquids contained in it are not expelled. An effective use of this device is only possible with special consideration and determination of the distribution of the pressure surge in the collecting channel.
The document with publication number U.S. Pat. No. 6,196,664 B1 discloses a device for delivering ink jets for printers in which inkjets can be delivered from outlets. These outlets are supplied with ink via secondary channels which are connected to the main channel. The delivery of ink is caused by several pressure generation means in the form of piezoelectric elements, such a piezoelectric element being assigned to each outlet. The assignment of a piezoelectric element to each outlet is necessary since the outlets must be triggerable separately from one another to produce different print formats.
The device described in the documents becomes technically complex due to the assignment of one piezoelectric element to each of the outlets.
Furthermore, the document with publication number US 2001/0038402 discloses a device in which there are outlets, which are located in a two-dimensional grid and through which droplets can be discharged from the device. The outlets that are arranged in a grid shape are connected via secondary channels to the main channel. A pressure surge on one side wall of the main channel can be transferred to the wall of the main channel for example by mechanical pressure and from there to the secondary channels which expel droplets of the liquid which fills the main channel and the secondary channels via the outlets. For this purpose these outlets have piezoelectric elements, which can open or close the outlets so that each of the outlets via which droplets are delivered can be determined individually. This is necessary for example for a use of the device as claimed in the invention as the printing head for inkjet printers in order to be able to produce different print formats.
The pressure which is applied to eject liquid onto the side wall of the main channel acts in the lengthwise direction of the secondary channels and perpendicular to the direction of primary extension of the main channel. The side wall is supported at least on one end. At the same time, the pressure which is applied to the side wall is uniform over the length of the side wall. Part of the force which acts on the side wall is accommodated here by the support of the side wall, another part leads to deflection of the side wall. In this way the side wall is deflected differently in individual sections; this causes a locally different pressure wave in the main channel. The pressure distribution within the main channel and accordingly also the secondary channels is therefore different, which leads to different amounts being expelled via the outlets. Metering with relative accuracy as is known for example from document WO 99/42805 is not possible with the device according to document US 2001/0038402 A1.
Finally, the prior art discloses a document with publication number WO 02/060582 A2. This publication discloses microfluidic devices for dispensing liquids from a microfluidic system. The document discloses a host of so-called peristaltic pumps by which a liquid can be advanced in a channel. In doing so, at successive locations in a time sequence a pressure surge is applied to the wall of the channels, which is moving the liquid in the channel in the two lengthwise directions of the channel. The liquid can thus be advanced in a preferred lengthwise direction by the pressure surges, which are matched in time. In FIGS. 8a and 8b a device is disclosed in which there are several channels next to one another which are exposed in parallel to pressure surges in order to advance a liquid at the same time in the channels. Metering with this device is not possible.
Therefore it is an object of the invention is to provide a device for parallel metering of a liquid of the initially mentioned type in which all secondary channel arrangements can be uniformly emptied even if a pressure surge is acting in time with different delays on the secondary channels or the secondary channel arrangements.
Another object is to provide a device, which is made technically less complex and with which parallel metering of small amounts of liquid with relative accuracy is possible.
An object of the invention is furthermore to provide a device which is simple to handle, suitable for operation by automatic devices, economical to produce, and which is suited to the materials used and as a disposable article.